Nano-patterning is an essential part of nanotechnology research and is used to fabricate nanostructures to harness their unique properties. However, in order for nano-device and nanostructure fabrication to have significant practical value, a low-cost and high-throughput nano-patterning technique is needed. Among many new emerging lithography techniques that are aimed at addressing this issue, nanoimprinting techniques are regarded as one of the most promising.
Nanoimprint lithography (NIL) is a nano-scale lithography technique where a surface relief pattern on a hard mold is physically imprinted into a thermal plastic polymer film at elevated temperature and pressure. Nanoimprint lithography has attracted more and more attention in both research and commercial applications due to its potential application in nano-scale patterning. It is often desirable because of its sub-10 nm resolution and simple equipment setup requirements. Nanoimprint lithography is further a relatively simple process that has high throughput, thus enabling low-cost, large-scale patterning of nano-structures.
Although nanoimprint lithography has proved to be very successful in nano-patterning, especially in replicating nano-scale features with uniform sizes, it still suffers from several limitations as a flexible lithographic technique. A preferred lithographic technique should be capable of producing both large and small features in various combinations and distributions, which is a typical requirement in micro- and nano-fabrication processes. For example, in the case of imprint lithography (such as nanoimprint lithography), mold features on the mold are physically pressed into a polymer. Larger features on the mold must displace more polymer material over larger distances. Thus, patterns with large features are much more difficult to imprint than smaller features (also known as nano-patterns). Furthermore, defects or pattern failures in the form of incomplete pattern transfer can occur due to the high viscosity of the polymer melt and the mold pattern complexity.
On the other hand and separate from nanoimprint lithography, photolithography is a well-developed process and has been pushed towards its limit to maintain its role in future microelectronic fabrication. In most cases, the cost of these next generation photolithography systems is prohibitive, except for large-scale production runs.
The present invention combines the processing steps of nanoimprint lithography and photolithography to provide a new technique that provides many new advantages. That is, the present invention enables patterning of both large-scale and sub-micron size structures in a single step. With many advantages, the present invention may be used in the fabrication of a wide range of nano-scale electronic, photonic, and biological devices where patterns of various sizes and densities are needed.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.